1. Field of the Invention
The present invention is directed to a defibrillator/cardioverter having a plurality of n (n being greater than or equal to three) electrodes which are connected to a means for generating electrical pulses.
2. Description of the Prior Art
A defibrillator/cardioverter is disclosed in German OS 39 19 498, wherein one of a plurality of electrodes is arranged in the interior of the heart, and the other electrodes are placed outside at the heart. Either directly, or via discharge distances which form a short-circuit for high voltages, the outer electrodes are electrically connected to each other and are connected to a first of two output terminals of the pulse generator. The electrode disposed inside the heart is connected to a second output terminal. Upon the generation of an electrical pulse as an output signal by the pulse generator, the electrical current density is distributed in the heart muscle according to the placement of the electrodes and thereby preferably penetrates the thickest zones of the heart muscle, which form the principal part of the heart muscle mass, in order to achieve successful defibrillation or cardioversion.
Another defibrillator is disclosed in U.S. Pat. No. 4,548,203, having a plurality of electrodes which are connected in pairs to different outputs of a pulse generator, and are disposed at different locations relative to the heart, which are preferably on opposite sides of the heart. For defibrillation, the individual electrode pairs are successively charged with an electrical pulse via the outputs of the pulse generator. The spatially and chronologically separated pulse output is intended to reduce the energy required for successful defibrillation.
In the aforementioned defibrillator disclosed in German OS 39 19 498, the distribution of the current in the heart can be set only on the basis of the positioning and size of the individual electrodes. The positioning of the electrodes, more specifically their spacing relative to each other and relative to the heart, is, however, limited by anatomical conditions. Moreover, an electrode is required inside the heart, and an extremely high current density arises in close proximity to this electrode, so that damage to the heart tissue is possible in the event of an unfavorable placement of this inner electrode, or a dislocation of this inner electrode.
In the defibrillator disclosed in U.S. Pat. No. 4,548,203, distribution of the current density to different zones of the heart muscle is not possible, because only two electrodes simultaneously participate in the pulse delivery.